This application relates to a mold which is adapted to simultaneously mold a closure having a threaded port, plus a separate, threaded plug adapted for sealing the port. As the mold opens, the plug is screwed into the port so that the complete closure is provided in a single shot.
Threaded port closures are used for large cans, for example, five-gallon paint cans, and large containers of industrial chemicals and the like.
It is, of course, a major labor-saving improvement to mold the closure with its threaded plug seated in the port, avoiding the need for installation of the plug. However, added advantages are also provided by this invention. For example, since the plug and the closure are molded simultaneously out of the same molding compound, their rates of shrinkage can be expected to be identical, so there is no problem of fitting the plugs to the threaded ports, as may take place when a plug is molded in a separate operation. In that case, due to unequal shrinkage of the two parts on cooling because of the use of different lots of molding compound, or due to differing molding conditions, the plug may not fit the port.
The invention of this application may be adapted to injection molds and other mold types as may be desired, to provide the high speed molding of threaded port closures and their threaded plugs, installed therein in a single molding operation.